Amanda Knox

Amanda Knox talks to the press surrounded by family outside her mother's home in Seattle, Washington

Amanda Knox talks to the press surrounded by family outside her mother's home in Seattle, Washington March 27, 2015. Italy's top court on Friday annulled the conviction of American Amanda Knox for the 2007 murder of British student Meredith Kercher and, in a surprise verdict, acquitted her of the charge. The Court of Cassation threw out the second guilty verdict to have been passed on Knox, 27, and her Italian former boyfriend Raffaele Sollecito for the lethal stabbing. REUTERS/Jason Redmond

Italy's top criminal court has scathingly faulted prosecutors for presenting a flawed and hastily constructed case against Amanda Knox and her former Italian boyfriend, saying Monday it threw out their convictions for the 2007 murder of her British roommate in part because there was no proof they were at the crime scene.

The Court of Cassation issued its formal written explanation, as required by Italian law, for its March ruling vindicating the pair once and for all in the murder of Meredith Kercher, in the apartment the two women shared while students in Perugia, Italy.

The court wrote there was an "absolute lack of biological traces" of Knox, an American, or co-defendant Raffaele Sollecito in the room or on the victim's body. Slamming the quality of the prosecution's case, the court cited "blameworthy omissions of investigative activity."

Media clamor also was a factor in what was ultimately a flawed case, the high court concluded.

"The international spotlight on the case in fact resulted in the investigation undergoing a sudden acceleration, that, in the frantic search for one or more guilty parties to consign to international public opinion, certainly didn't help the search for substantial truth," the judges wrote.

The high court in March declared that Knox, now 28, and Sollecito, now 31, didn't murder the 21-year-old Kercher, a stronger exoneration than merely finding there was insufficient evidence to convict.

Had the Cassation Court upheld the 2014 appeals court convictions of the pair, Knox would have faced 28½ years in an Italian prison, assuming she would have been extradited from the United States, while Sollecito had faced 25 years.

Knox and Sollecito had served nearly four years in Italian prison after a first, lower court conviction by a Perugia court. (AP)